ts-polymorphism.ts

interface Shape {
    getArea: () => number
}

class Circle implements Shape {
    constructor(private radius: number = 0) {}
    getArea() {
        return Math.PI * this.radius * this.radius
    }
}

class Rectangle implements Shape {
    constructor(private width: number = 0, private height: number = 0) {}
    getArea() {
        return this.width * this.height
    }
}

function printArea(s: Shape) {
    console.log(s.getArea())
}

printArea(new Circle(2))
printArea(new Rectangle(2,3))